Wheelchairs generally include a seat assembly mounted to a wheelchair frame and two armrest apparatuses positioned adjacent to and on opposing sides of the seat. These armrest apparatuses generally provide the occupant support during ingress and egress from the wheelchair. Just as importantly, though, armrests provide comfort and convenience for the occupant by furnishing a fixture upon which they may rest their arms. Hence, the prior art armrests, as shown in FIG. 1, are often height-adjustable and/or removable from the wheelchair to accommodate a variety of different sized and shaped persons.
Typically, height-adjustable armrest apparatuses 10 include an armrest base frame 11 rigidly secured to a portion of a wheelchair frame 12 adjacent a seat (not shown). Armrest apparatus 10 usually includes an armrest pad 14 which is carried by an inverted, U-shaped, pad support frame 13. This support frame 13 includes a horizontal tube portion 15, supporting the pad, and a pair of vertical posts 16 extending downwardly from opposite ends of the horizontal tube portion. Each post 16 is oriented in a substantially vertical manner for ease of mounting and height adjustment relative to armrest base frame 11.
Base frame 11 usually includes a pair of spaced-apart upwardly extending receiving tubes 17 each having post receiving bores 18 dimensioned to slidably and telescopically receive the distal ends of the corresponding post portions. Hence, the height of armrest pad 14 can be adjusted by moving posts 16 reciprocally in or out of the corresponding receiving bores 18. A releasable locking latch 19 is usually provided to lock support frame relative to base frame 11 after height adjustment has been made.
While these two-post height-adjustable armrest apparatuses 10 provide added lateral mounting stability, several problems are inherent with these designs. For example, these armrest apparatuses are difficult for quadriplegics (i.e., those severely impaired) to manipulate. While attempting to adjust the height of pad support frame 13, those with limited physical capabilities are often unable to telescopically retract or extend both posts 16 simultaneously into or out of the corresponding receiving bores 18 in a smooth even manner. Hence, this skewed motion causes posts 16 to lodge or jam in the corresponding receiving bores 18.
Moreover, once the occupant applies a force sufficient to dislodge the posts from their skewed orientation relative the receiving bores, the momentum often completely separates the pad support frame from the base frame. Thus, the occupant is burdened with the prospect of reinstalling the posts back into the corresponding bores. This task is troublesome since the occupant may experience alignment difficulties between the posts and the corresponding receiving bores, particularly if support frame 13 should be dropped during handling. Should this occur, substantial bending may be required in order to reinstall the armrest. This problem can be magnified for those users who are severely physically impaired.
Another problem associated with prior two-post armrest apparatuses is that they do not facilitate interchangeability of the armrests. Sometimes, the user may find it desirable to increase or decrease the length of the armrest support frame. With the current two-post armrest apparatuses once base frame 11 is mounted to wheelchair frame 12, only those armrests support frames having post ends properly corresponding to the distance between the post receiving bores of the receiving tubes may be installed.
Single-post height-adjustable armrest apparatuses (not shown) have been developed to overcome the above-mentioned problems associated with the two-post assemblies. Typically, the single post is telescopically received in a receiving bore which, in combination, functions both as a height adjustment mechanism as well as an armrest assembly mounting mechanism. Hence, when the tolerances between the post and the bore are too small, the pad support frame often becomes lodged in the receiving bore. Accordingly, similar to the two-post assemblies, when the occupant attempts dislodge the post, they often inadvertently remove the post completely out of the receiving bore. In contrast, when the tolerances are too large (i.e., to reduce jamming therebetween), the post tends to rattle and move about the receiving bore causing the pad support frame to feel unstable.